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Old 04-14-2019, 04:38 PM   #241
kognito
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Had to check this thread. every once in a while Youtube puts up a silly alert on my tablet asking me if i want to see someone's stupid video projected onto my livingroom TV. (usually happens after every time I reboot my tablet)

Ten minutes ago, I rebooted and was asked if I wanted to see an RX8 with a turbochargered engine autocross.

Unfortunately this time the link to my TV failed, so I couldn't tell if someone filmed you or not
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Old 04-14-2019, 05:36 PM   #242
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Cool! Pretty amazing that after custom building an entire drivetrain it’s the suspension that presents the greatest needs.
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Old 04-14-2019, 05:42 PM   #243
John V
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I think I just made it too stiff
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Old 04-14-2019, 10:04 PM   #244
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How the turbo? Laggy? No biggie?
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Old 04-15-2019, 05:33 AM   #245
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Not laggy when exiting corners with reasonable revs (3k+). That lot was so tiny and it was so slippery I was leaving some corners around 2400 and the turbo is stalled there, so no boost. I think it's going to be very very good.
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Old 04-15-2019, 07:06 AM   #246
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The progress looks very promising! I saw your video elsewhere, so now I can't wait to see this thing in action.
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Old 04-15-2019, 10:20 AM   #247
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So amazing. Congrats!
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Old 04-17-2019, 07:19 AM   #248
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So. Takeaways from the first shakedown of the car, and next steps in this process.

1) Boost control wasn't working during the test event. That's because I screwed up and connected the wastegate actuator incorrectly. I'm kind of lucky I didn't blow an engine - but the Haltech saved my bacon. I effectively had no boost control at all, making the power delivery very abrupt and keeping the turbo wastegate closed.

2) The car is too low and it felt like the front suspension was not working well. It felt way too stiff, but with the springs and front bar I have on it, it should have been okay.

3) The rear diff puked some fluid after a bunch of back-to-back runs. It vented through the vent hole at the top of the diff, which is what it should do, but I need to address the fluid leakage somehow because it's not good to dump fluids on the course.

4) It has an oil leak at the pan

Fixes:

1) This one is easy. I use a four-port solenoid to control the two-port wastegate actuator. The way the wastegate actuator works is there is an internal spring and an upper and lower chamber separated by a diaphragm. If you cap the lower part of the diaphragm and connect the upper port to the pressure side of the turbo, you have traditional boost control. As the turbo develops boost, it builds pressure in the upper chamber of the wastegate actuator, which pushes against the internal spring and moves a rod which opens the wastegate. The internal spring force (seven pounds in my case) is what boost level you'll run. If you want higher boost pressure, you can install a controlled leak in that line, which can be controlled by a solenoid. If you bleed off pressure (say 2psi) to the actuator, it will raise your boost level by 2 psi.



A better way to solve the problem and a way to get faster turbo spool-up is to re-direct some of that turbo pressure to the bottom port of the wastegate actuator. The more pressure that is diverted to the lower chamber, the higher boost pressure you'll run. What is really bad is diverting ALL of the pressure there, so that as boost pressure increases, the wastegate gets pulled shut and can never open. Which is what happens if you connect the hoses wrong.

2) I found a bind in the front suspension. The only bushings in the car that aren't spherical bearings are in the upper control arms. They're offset Delrin bushings in this case, and they were clamped so hard the upper control arms couldn't move. Easy fix. I'm also raising the front and rear about 1/2". This will give more compliance over bumps and it should fix the bottoming out issue.

3) I'm adding a small catch can to the rear diff vent tube, so the fluid has a place to go.

4) I removed the oil pan (annoying, but still easier than on the BMW!) and took it to a buddy. When the baffles and trap doors were welded into the pan, they overheated one of the welds and created a tiny crack. I stress-relieved the crack and had a buddy weld it over with a bead of filler. It shouldn't crack again and that should eliminate my oil leak.

Next event is a test and tune at a much bigger site on Saturday. I should be able to get 20-30 runs at this event and really shake the car down.
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Old 04-18-2019, 09:14 AM   #249
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Quote:
Originally Posted by kognito View Post
Had to check this thread. every once in a while Youtube puts up a silly alert on my tablet asking me if i want to see someone's stupid video projected onto my livingroom TV. (usually happens after every time I reboot my tablet)

Ten minutes ago, I rebooted and was asked if I wanted to see an RX8 with a turbochargered engine autocross.

Unfortunately this time the link to my TV failed, so I couldn't tell if someone filmed you or not
This is crazy John. The youtube video prompt appeared again this morning, and this time it did play. It was your video. It was a run you recorded where at the end, in the paddock, someone says something about a wiring harness drooping or draging?

I call it crazy as I have never accessed this forum on my tablet. we are not facebook connected, just a random pop up and it happens to be of your car video.

And I see what you meant about the rough ride
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Old 05-14-2019, 07:08 AM   #250
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Minor update. I needed to do some cooling system upgrades, the car would get very hot after a single fourth-gear pull on the dyno or at the test events. The radiator was clearly undersized, and I didn't have it well ducted. The factory RX-8 ducting is actually very efficient, I've learned. The factory ducting is accomplished using the undertray, which prevents air from flowing under the radiator, and also the vertical members of the undertray, which prevent air from flowing around the radiator. I didn't install the undertray, because it didn't really fit anymore with all the work I had done. Well... I needed to make it fit. After a few hours of cutting and working to seal everything up, here is how the ducting looks. This is all using factory parts modified to fit. The openings on either side of the intercooler go directly into the radiator. There is no escape path other than through the radiator because I foamed off the sides of the radiator where it meets the vertical elements of the undertray as well as the top of the radiator where it meets the top of the core support. The bottom of the radiator is foam-sealed to the plastic undertray, which is fastened to the subframe at the rear.



Here is a view inside one of the ducts.



So now air that flows through the intercooler must flow through the radiator and there are two large flow paths around the intercooler that also must flow through the radiator. I also purchased a radiator with three times the volume of the tiny stock one, and put in a new coolant reservoir and pressure cap. After a long dyno session this weekend, no issues running hot at all. So I'm going to declare success on that.

We spent about four hours on the dyno Saturday. First we got the variable valve timing on the intake cam working reliably. We added some ignition timing and picked up a good amount of part-throttle response, which should make the car snappier on course. With the aggressive cams I have, and only 9.7:1 static compression and E85 fuel it's not likely this engine will ever preignite the fuel mixture. At some point I'd like to build an engine closer to 11:1 compression, but for now this makes plenty of power and has good response.

I also discovered a problem with my fuel system where fuel is not being siphoned from the right half of the fuel tank (saddle style with two reservoirs). We fuel starved on the dyno a couple of times at only 1/4 tank of fuel, because all the fuel was on the other side. I need to get that worked out but in the near term I'll just run the car with a full tank.

We ended up spending most of our time tuning the boost controller, so we were doing part-throttle runs. At 60% throttle we get full turbo spool, which is awesome... 60% throttle and 8psi of boost was 320 horsepower at the wheels, which is just crazy. It should make around 450 at the wheels on 14psi of boost, so I need to make sure not to turn it up that high

I'm towing the car out to Lincoln in a week and a half, which is insane because it'll be my first competition event in the car. I'm about a month behind where I need to be. But hey, if I go out there and the car doesn't make a single good run at least I'll have a weekend with friends and I'm sure I can find something else to drive!
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